1. Field of the Invention
This invention generally relates to the art of generating electrical energy and has particular reference to a compact mechanically-powered electric generator that is adapted for use in a photographic camera or other apparatus which requires a small but reliable source of electricity.
2. Description of the Prior Art
Photographic cameras having mechanically tripped and powered devices that generate electrical energy for firing photoflash lamps or operating other devices associated with the camera are known in the art. A camera having such an electric generator wherein a voltage pulse is produced by a flat coil of wire that is attached to the camera shutter and propelled into the gap of a permanent magnet when the shutter is tripped is disclosed and claimed in U.S. Pat. No. 3,709,118 issued Jan. 9, 1973 to the present inventors. The "built-in" electric generator replaces the battery normally employed in the camera and thus eliminates the problems encountered in firing a photoflash lamp when the batteries become weak or dead, or the battery contacts become dirty or oxidized.
A camera having a flap-type shutter with a permanent magnet that enters a stationary wire coil when the shutter is actuated and thus generates a voltage pulse which "fires" a thyratron tube in an external electrical circuit which flashes a gaseous discharge lamp is described in U.S. Pat. No. 2,538,577 issued Jan. 16, 1951 to C. W. McCarty. A camera having a magnetic circuit with an oscillating core element which generates a voltage and fires a photoflash lamp when the shutter is actuated is disclosed in U.S. Pat. No. 3,480,808 issued Nov. 25, 1969 to H. F. Reith. A camera shutter and electric generator assembly wherein the voltage is produced by a rotor that is rotated when the shutter is actuated is disclosed in U.S. Pat. No. 3,703,132, issued Nov. 21, 1972 to D. E. Beach.
Various other types of electric generators that produce a voltage in response to changes in the flux density or flux distribution in a magnetic circuit are disclosed in U.S. Pat. No. 2,426,322; 2,784,327; 2,904,707; 3,065,366; and 3,500,086.
Camera flashguns having an integral electric generator consisting of a permanent magnet and a pivoted armature that is manually actuated by a shutter-release cable or powered by a leaf spring are disclosed in U.S. Pat. Nos. Re. 22,433; 2,448,897 and 2,490,225.
Instant-photographic type cameras which are collapsible are also well known in the art. A fully automatic single-lens reflex camera that is foldable into thin compact size suited for convenient carrying in a pocket of the photographer is disclosed in U.S. Pat. No. 3,714,879 issued Feb. 6, 1973 to Edwin H. Land et al. Motive power for such cameras is derived from a high-speed electric motor that is energized by a battery which constitutes part of the film cassette that is inserted into the base portion of the camera. Cameras of this type are known in the art as "SX-70" Land cameras and are presently being marketed by the Polaroid Corporation. The various components and features of such cameras and the new instant-developing film which they employ are described in the January 1973 issue of "Popular Science" magazine (pages 84-87 and 114).
In view of the added cost of the disposable battery and the potential problems of weak or dead cells and dirty contacts traditionally associated with the use of batteries in cameras, it would be very desirable from both an economical and operational standpoint to provide a compact mechanically-actuatable electric generator which can be used in such collapsible instant-photographic type cameras in lieu of a battery.